Consolidated Statements of Cash Flows - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			5 Months Ended	6 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2014	Sep. 30, 2014		Sep. 30, 2013	Jun. 03, 2014	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2015	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income (loss)	$ 373	$ (306,356)	[1]	$ (1,284)	$ (22,956)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization		73,745		53,989
Accretion of liability for asset retirement obligations	2,022	6,181		6,266	11,771	$ 12,279		$ 17,788		$ 23,400	$ 28,299
Deferred income taxes	219				4,495					(459,223)	49,687	$ 29,900
Exploration expenditures					26,300						800
Impairments of oil and gas properties					100	690,300				1,678,800	2,900	8,900
Goodwill impairment		329,293		12
Gain on sale of assets				(1,745)
Changes in operating assets and liabilities:
Net cash provided by operating activities	22,209				105,122
Cash flows provided by (used in) investing activities:
Net cash used in investing activities	(200,929)				(258,714)
Cash flows provided by (used in) financing activities:
Net cash provided by (used in) financing activities	(15,729)				344,830
Net increase (decrease) in cash and cash equivalents	(194,449)				191,238
Cash and cash equivalents at beginning of period	200,050	5,601		3,885	8,812	5,601	$ 3,885	5,601	$ 3,885	5,601	1,521
Cash and cash equivalents at end of period	5,601				200,050		8,812				8,812	1,521
Successor Company [Member]
Cash flows from operating activities:
Net income (loss)	373	(306,356)				(760,968)		(1,056,601)		(1,653,866)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	22,775	73,745				162,292		235,641		314,953
Accretion of liability for asset retirement obligations	2,022	6,181				12,279		17,788		23,400
Change in fair value of derivative instruments	9,528	(20,045)				(14,657)		(13,043)		(11,106)
Deferred income taxes	219	12,847				(238,010)		(419,997)		(459,223)
Impairments of oil and gas properties						690,312		1,094,566		1,678,804
Goodwill impairment		329,293				329,293		329,293		329,293
Amortization of deferred financing costs and discount on debt	(841)	(2,534)				(5,104)		(7,688)		(10,996)
Changes in operating assets and liabilities:
Trade accounts receivable	18,238	6,410				9,721		19,267		20,205
Prepaid expenses	3,274	(5,873)				16,461		20,702		25,008
Other assets		174				301
Accounts payable and accrued expenses	(29,592)	(23,804)				(70,981)		(90,559)		(77,209)
Asset retirement obligation settlements	(3,787)	(7,190)				(32,038)		(39,025)		(53,256)
Net cash provided by operating activities	22,209	62,848				98,901		90,344		126,007
Cash flows provided by (used in) investing activities:
Property acquisitions	(141,886)	(260)				(350)		(350)		(350)
Capital expenditures	(58,976)	(111,136)				(239,090)		(271,496)		(298,849)
Other property and equipment additions	(67)	(40)				(58)		(58)		(58)
Proceeds from sale of assets										5,000
Net cash used in investing activities	(200,929)	(111,436)				(239,498)		(271,904)		(294,257)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness	475,000
Repayments of indebtedness	(475,000)							(325,000)		(325,000)
Proceeds from intercompany promissory note								325,000		325,000
Payments on put financing										(1,751)
Advances to EGC	(15,729)	43,010				135,480		177,832		165,768
Deferred financing costs								(1,089)		(1,151)
Other								(689)
Net cash provided by (used in) financing activities	(15,729)	43,010				135,480		176,054		162,866
Net increase (decrease) in cash and cash equivalents	(194,449)	(5,578)				(5,117)		(5,506)		(5,384)
Cash and cash equivalents at beginning of period	200,050	5,601				5,601		5,601		5,601
Cash and cash equivalents at end of period	5,601	$ 23			200,050	$ 484		$ 95		217
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Capital contribution from EGC	95,000
Derivative instruments premium financing										5,115
Changes in capital expenditures accrued in accounts payable	(27,404)									(80,984)
Non-cash change related to property disposition										(64,295)
Non-cash changes in asset retirement obligations										52,842
Interest	1,559									$ 52,146
Predecessor Company [Member]
Cash flows from operating activities:
Net income (loss)				(1,284)	(22,956)		(13,342)		(11)		85,274	58,810
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization				53,989	85,127		100,501		146,146		200,359	113,581
Accretion of liability for asset retirement obligations				6,266	11,771		16,101		23,098		28,299	15,565
Change in fair value of derivative instruments				26,478	(6,996)		48,184		44,438		20,884	9,491
Non-cash compensation				1,910	19,704		3,896		6,321		7,344	4,717
Deferred income taxes				(1,052)	4,495		(6,604)		1,025		49,687	29,900
Exploration expenditures				73	14,825		1,829		1,876		5,520	4,227
Impairments of oil and gas properties					61		766		827		2,937	8,883
Goodwill impairment				12
Amortization of deferred financing costs and discount on debt				1,361	2,359		2,741		4,149		5,396	2,556
Gain on sale of assets				(1,745)			(1,825)		(1,825)		(28,681)
Other				22,562	(573)		21,815		20,905		27,235	2,448
Changes in operating assets and liabilities:
Trade accounts receivable				8,542	(21,106)		8,344		(8,433)		(1,916)	(33,547)
Prepaid expenses				549	(1,881)		7,938		11,057		2,871	1,192
Other assets				(1,361)			506
Accounts payable and accrued expenses				10,457	52,932		30,770		50,034		35,658	31,477
Asset retirement obligation settlements				(10,072)	(32,640)		(26,537)		(41,584)		(53,308)	(35,429)
Net cash provided by operating activities				116,685	105,122		195,083		258,023		387,559	213,871
Cash flows provided by (used in) investing activities:
Decrease in restricted cash				51,757			51,757		51,757
Property acquisitions				(24,897)	(60,495)		(25,478)		(83,412)		(27,560)	(578,372)
Deposit for Nexen Acquisition							(7,040)		(7,040)		(7,040)
Capital expenditures				(100,021)	(197,968)		(169,936)		(268,905)		(322,040)	(184,850)
Other property and equipment additions				(254)	(251)		(753)		(984)		(2,016)	(1,743)
Proceeds from sale of assets							80		80		52,317
Net cash used in investing activities				(73,415)	(258,714)		(151,370)		(308,504)		(306,339)	(764,965)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness					345,000							509,313
Repayments of indebtedness				(40,000)			(35,000)		55,000		(65,000)	(20,000)
Deferred financing costs				(32)	(170)		(36)		(206)		(674)	(8,469)
Purchase of shares into treasury				(4,544)			(4,544)		(4,544)		(9,640)	(8,798)
Exercise of stock options				360			794		794		1,385	441
Net cash provided by (used in) financing activities				(44,216)	344,830		(38,786)		51,044		(73,929)	472,487
Net increase (decrease) in cash and cash equivalents				(946)	191,238		4,927		563		7,291	(78,607)
Cash and cash equivalents at beginning of period	$ 200,050			3,885	8,812		3,885		3,885		1,521	80,128
Cash and cash equivalents at end of period				$ 2,939	200,050		$ 8,812		$ 4,448		8,812	1,521
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Changes in capital expenditures accrued in accounts payable					40,884						13,819	27,621
Non-cash changes in asset retirement obligations					7,415						25,773	23,518
Interest					$ 23,185						$ 47,339	$ 21,129

[1] Included in costs and expenses for the three months ended September 30, 2014 is goodwill impairment of $329.3 million.